Clopidogrel hydrogen sulphate is an anti-platelet drug. Both the racemic form of the drug and optical isomers are known in the art. See, e.g., U.S. Pat. Nos. 6,429,210 and 4,847,265. The '210 patent discloses that clopidogrel hydrogen sulphate can exist in two polymorphic forms (designated as Form I and Form II) and provides analytical characterization for the polymorphs.